diff --git a/requirements.txt b/requirements.txt
index 5a499ed..d5504c1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,7 +7,7 @@ h5py==2.9.0
 kiwisolver==1.1.0
 matplotlib==2.2.4
 networkx==2.2
-nltk==3.4.5
+nltk==3.6.6
 numpy==1.16.4
 pandas==0.24.2
 Pillow==6.2.0